One problem you may be facing since they started to thaw, then were refrozen in bulk is they may be sort of stuck together a bit. Personally I'd do a test. Remove one rat, heat it as you normally would for feeder use, give it the sniff test over a few moments to see if you can detect any whiff of the sweet smell of decomp. Let it cool, rewarm it again immediately, sniff it again (if you aren't sensitive to smells ask someone to help you do this).

If you can't smell anything nasty then I would think you'd be good to go. However, if there's any worry in your mind that these rats started to go off - toss them and call it a lesson learned.